Various droplet ejecting printer technologies have been or are being developed. One such technology, acoustic ink printing (AIP), uses focused acoustic energy to eject a marking material (generically referred to herein as ink) onto a recording medium. For a more detailed description of acoustic ink printing, reference may be made to U.S. Pat. Nos. 4,308,547, 4,697,195, and 5,028,937, and the citations therein.
A concern in AIP printing is keeping debris, such as paper dust, from contaminating the droplet ejectors and thereby reducing print quality. Contamination may affect the droplet ejectors in at least three ways. First, debris can disturb the location of the free surface of the ink, thereby disturbing the very important spatial relationship between the acoustic energy's focal area and the free surface of the ink. Second, debris can partially or completely block the path between the ink and the recording medium. Third, debris can disturb the internal flow path of the ink inside the droplet ejector, preventing replenishment of ejected ink.
Thus, cap structures which alleviate debris contamination of print quality are beneficial. Such structures are even more beneficial if they can be fabricated at low cost. Preferably, such capping structures should be removable to allow cleaning.